And the chances range from 30% down to less than 1% of being successful, i.e., 30% is for time on
This translates into a lot of "Thank you for your interest" and "We regret to inform you" emails (and letters still sometimes). There is a lot of disappointment in the work. It is inherent to a profession that is creative and to a level, competative. There is no infinite amount of funding, there is an infinite amount of interesting Universe out there.
I have become quite Zen about it (ask me again when this postdoc is running out) and in part this is because the writing by Will Wheaton. He is in a creative profession. He pitches himself a lot. He gets rejected a lot (like every time right after Star Trek it seems). But he stuck with it.
But the importance of the sales pitch and the inherent rejection is something we might want to warn starting grad students about.